Ultrasound and freeze-thaw modifications of cassava starch: Microstructure, functionality, and 3D printing potential

Starch, used in various applications; offers restricted utilities due to the limited functionalities in its native form. Several methods have been explored to enhance its functionality. Among these, non-thermal processes such as ultrasound (US) and freeze-thaw (FT) cycles impact starch properties, making them promising processes for emerging applications. In this study, starch (50%, w/v in distilled water) was processed (either individually or combined) using US at different amplitudes (70, 80, and 90%) for 30 min at room temperature, and multiple FT (1, 3, and 5) at -40°C for 3 hr per cycle. Amylose content (AC), water holding capacity (WHC), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were measured. The suitability of modified starches for 3D printing was also evaluated. The treatments resulted in modified starches with a decrease in AC varying from 19.5% to 17.1%, and an increase in WHC ranging from 53.7% to 66.1% (p<0.05). The modified starches exhibited enhanced pasting properties, indicating improved thermal stability and gelation ability. SEM showed increased surface deformation in modified starch granules compared to the smooth surfaces of those unmodified. XRD patterns showed typical A-type peaks; however, starches subjected to combined treatments exhibited a reduction in relative crystallinity. The use of the starches for 3D printing showed that the modified starches had a more defined surface compared to native starch. Therefore, the combined US and FT treatments can be applied to enhance functionality and 3D printability of cassava starch, opening new avenues for its use as a functional material for food development. • Ultrasound and freeze-thaw treatments affected the microstructure of starch granules. • Modified starches displayed enhanced pasting behavior compared to native starch. • Crystalline and amorphous regions of starch were affected by the treatments. • Slight decreases in resistant starch were observed in the modified starches. • The combined treatments improved the 3D printability of cassava starch.